The present invention relates to improvements in electrophoresis plates. By way of background, electrophoresis is a well-established method for separation of charged macromolecules or colloidal particles and is useful in the analysis of proteins found in complex physiological fluids and tissue. Typically, electrophoresis is carried out in a separation medium, for example a polymer gel, such as agarose or polyacrylamide. Of course, cellulose acetate is also used as a separation medium.
In the formation of an electrophoresis plate, the electrophoretic or polymer gel is cast in a mold and secured to an inert substrate. In the electrophoresis process, numerous samples are typically placed on the electrophoretic medium, i.e., the polymer gel. To effect electrophoretic separation, an electric field is established with respect to the gel containing the samples.
Various fluids may be added to the gel during the electrophoretic separation, such as solvent or buffer. When providing fluid to the plate for the electrophoretic process, different means have allowed fluid to be delivered at one end of the plate and removed from the other. For example each end of the electrophoresis plate has been put into separate reservoirs. Alternatively fluid has been allowed to wick onto and off of opposite ends of the plate from separate reservoirs.
U.S. Pat. No. 4,892,639 describes another approach to delivering fluids to an electrophoresis plate by providing thickened regions at the respective ends of the plates. The thickened regions are made of the polymer gel and include a quantity of the fluid, e.g. buffer, to be delivered to the plate. This approach advantageously results in a self-contained electrophoresis plate.
During the electrophoretic process, certain phenomenon occur which may interfere with or adversely influence the electrophoretic separation, especially for electrophoresis plates having thickened ends. For example, a heat build-up is associated with the voltage gradient which develops during the process, causing water which is present in the gel to become more mobile and to flow. If there is excessive fluid flow, called electroendosmotic (EEO) flow, water is delivered to the electrophoresis plate from the thickened ends, with a blurring and broadening of the electrophoresis zones thus contaminating the electrophoresis zone and interfering with the analysis of the electrophoresed sample. Another problem which occurs as a result of heat build-up is the actual collapse of the thickened ends of the plate, which is referred to as gel melt. These are problems with typical commercial agarose gel media. Gel melt may even occur when a thin layer of agarose gel is placed on a substrate and electrophoretic separation is performed using the aforementioned wicking approach to add fluid to the plate without the use of buffer blocks.
The present invention provides a solution to these problems pertaining to electrophoresis plates, as will be hereinafter described.